1. Field of the Invention
The invention relates to a method for determining traffic data, and to a traffic information center.
2. Discussion of the Prior Art
Methods exist for automatically producing traffic reports by assessing point-related data from stationary vehicle detectors, such as induction loops, in order to assess the traffic situation at or in the vicinity of the stationary detectors. In this case, data detected by a plurality of stationary detectors along, for example, a road section are collated in a center to form messages such as "three kilometer traffic jam between X.sub.18 and X.sub.2 ".
With regard to optimization of this system by determining traffic data on the basis of measurements from stationary detectors and mobile detectors (that is to say detectors which are also moving in the traffic), it is problematic that data from the two types,of detector are transmitted only at relatively long time intervals as a result of the telecommunications costs incurred for transmission to a center and that, owing to the limited number of stationary and mobile detectors, the data are transmitted only at relatively long distance intervals. Furthermore, and in particular, the data supplied from these two data sources and relating to vehicle speeds differ since, for example, the mean speed of travel of this one vehicle in this time interval along a path travelled by this vehicle is transmitted by vehicles to a center after a time interval in each case, while the mean vehicle speed of a large number of vehicles passing a specific point in the traffic system, namely the location of the detector, is transmitted by a stationary detector to the center within a time interval which is, furthermore, often relatively short. Separate treatment of single-point-related data (originating from stationary detectors) and distance-related data (originating from mobile detectors) results in inaccurate and inconsistent reports relating to the traffic situation.
Existing approaches to determining traffic data, in particular traffic jam reports, on the basis of speed measurements from stationary detectors and from mobile detectors, namely traffic flow models, domain models, microscopic models, are highly complex and have not been tested much in practice; in addition, some of these existing methods require a certain amount of input data synchronism.